---
id: CVE-2021-3986
aliases:
  - GHSA-m982-h4f8-g4hf
  - PYSEC-2026-1232
title: >-
  Generation of Error Message Containing Sensitive Information in
  janeczku/calibre-web
summary: >-
  Generation of Error Message Containing Sensitive Information in
  janeczku/calibre-web
severity: medium
cvss: 4.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N'
vendor: calibreweb
product: calibreweb
ecosystem: pip
affected:
  - calibreweb < 0.6.15
patched:
  - calibreweb 0.6.15
published: '2024-11-15'
updated: '2026-07-07'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-m982-h4f8-g4hf'
references:
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2021-3986'
  - url: >-
      https://github.com/janeczku/calibre-web/commit/6f5390ead5df9779ac81fadefffb476e03f93548
  - url: 'https://github.com/janeczku/calibre-web'
  - url: 'https://huntr.com/bounties/394af194-61a7-4e33-b373-877d4c766fca'
tags:
  - osv
  - pip
epss: 0.00371
epssPercentile: 0.28213
ingestedAt: '2026-07-08T18:25:51.193Z'
---

## Overview

A vulnerability in janeczku/calibre-web allows unauthorized users to view the names of private shelves belonging to other users. This issue occurs in the file shelf.py at line 221, where the name of the shelf is exposed in an error message when a user attempts to remove a book from a shelf they do not own. This vulnerability discloses private information and affects all versions prior to the fix.

## Affected packages

- `calibreweb < 0.6.15`

## Remediation

Upgrade to a patched release:

- `calibreweb 0.6.15`